Never had any trouble with the glued welded seams on my all pvc (no f/g or al. bottom) at the bow,the problems were all at the aft end,and I suspect o/b motor forces were involved.
I did a lot of repair work on mine,10years old, before getting a new one. Towing advice from mfr was a bridle attaching at the 2 tubes, not from the central lifting/towing eye. I followed that, no probs. Made up my own bridle, very easy, using snap shackles to attach to the eyes.
Picking up on the f/g hull aspect, is the problem getting adhesion on the hull. Better prep? Good luck with it. How old is it?Imo they have a lifespan.
2005 Integrity 386 "Sojourn"